On Mon, Apr 17 2023 at 3:11P -0400, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote: > If we use bio_for_each_folio_all on an empty bio, it will access the first > bio vector unconditionally (it is uninitialized) and it may crash > depending on the uninitialized data. > > This patch fixes it by checking the parameter "i" against "bio->bi_vcnt" > and returning NULL fi->folio if it is out of range. > > The patch also drops the test "if (fi->_i + 1 < bio->bi_vcnt)" from > bio_next_folio because the same condition is already being checked in > bio_first_folio. > > Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> This fix is a prereq for this dm-crypt patch to use folios: https://patchwork.kernel.org/project/dm-devel/patch/alpine.LRH.2.21.2302161619430.5436@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ Mikulas explained why an empty bio is possible here: https://listman.redhat.com/archives/dm-devel/2023-April/053916.html Reviewed-by: Mike Snitzer <snitzer@xxxxxxxxxx>
